This invention relates generally to gas turbine engines, and, more particularly, relates to a diffuser case for a gas turbine engine combustor.
In a conventional axial flow gas turbine, air from the compressor section enters a diffuser of a combustor through a set of exit guide vanes. From the combustor, the air drives the turbine mounted immediately downstream thereof. The diffuser has basically an inner and outer case wall held together structurally by struts positioned in the annular flowpath between the inner and outer case walls. A flow splitter can also be positioned in or after the annular passage to divert air for cooling or other purposes. The thermal response of the outer case wall of the diffuser and the compressor are not compatible with the the response of the diffuser inner case wall. As a result of this incompatability, the connecting struts must be of substantial size to carry the resultant load. Additionally, the compressor's exit guide vanes must be floated in their mountings to avoid overstress under the above circumstances.
An example of a gas turbine combustor is shown in U.S. Pat. No. 4,098,074, entitled, "Combustor Diffuser For Turbine Type Power Plant and Construction Thereof", assigned to United Technologies Corporation. This particular diffuser has a splitter for diverting air to a burner and to a cooling section. In the passage leading to the burner section struts are connected to the inner case wall and to the splitter. Additional structural struts are formed between the splitter and the outer case wall in the cooling section. Struts placed in the passages impede the flow of air therethrough and thus the efficiency of the gas turbine. These connecting struts further add to the engine weight.
The present invention is directed toward a diffuser providing higher efficiency in which these undesirable characteristics are eliminated.